This paper numerically investigated the effect of the arrays of the delta-winglet vortex generators (DWVGs) pairs on the flow field and heat transfer characteristics of gas turbine blade tip internal surface. Six different arrangements including three inclinations (30°, 45°, 60°) and two aspect ratios of DWVGs are calculated at Reynolds numbers ranging from 6000 to 14,000. The internal cooling passage of gas turbines are simplified as two-pass U bend channel and the U bend channel without any tabulators are considered as Baseline. The detailed flow structure, the evolution of vortices and heat transfer performance over the tip internal surface are presented. The results show that the arrays of DWVGs placed on the tip internal surface have great influence on the tip flow and heat transfer. Small-scale vortices are induced by the DWVGs, which have negligible impact on the main flow. Due to the nature of 180-deg turn, the impingement-like flow contributes the highest heat transfer performance. But too many DWVGs placed on the attachment region will weaken the energy of main flow and therefore reduce the local heat transfer. Besides, the blocked DWVGs (BVG) will enhance the heat transfer at the center line, and the guided DWVGs (GVG) will extend the low-energy flow cluster and thus weakening the heat transfer intensity. The results of this study are useful for understanding the mechanism of heat transfer characteristics in a realistic gas turbine blade by using the arrays of DWVGs.

Some surrogate fuel models have been formulated based on gaseous combustion properties. While development of surrogate fuel for spray combustion is still in an exploratory stage, it is in a great demand to develop methods to validate the volatility performance and corresponding combustion properties of a surrogate fuel mixture based on real fuel’s behavior. Distillation experiment of Chinese aviation fuel RP-3 was carried out to reveal evolution of components and chemical functional groups during the vaporization process of a real fuel. Both liquid and vapor samples were analyzed using GC-MS and NMR. The variation of functional groups and volatility performance of surrogate were also investigated using a well-validated numerical model. The experimental results show that the chemical functional groups almost have no change and that the average carbon number in the gas phase increases throughout the distillation. On contrary, the functional groups of some existing surrogates varied greatly during their distillation processes in spite that their distillation curves match well with real fuel’s. A 24-component mixture is formulated to demonstrated possibility to match both distillation behavior and combustion properties during vaporization. This study provides some potential directions for developing a surrogate with its vaporization truthfully representing the vaporization of the target real fuel.

High thermal load on the turbine blade tip surface leads to high temperature corrosion and severe structural damage. One common way is to deliver a part of coolant through bleed holes onto the tip portion for cooling purpose. In this study, numerical simulations are performed to investigate the effects of rotation on the internal tip heat transfer in a simplified rotating two-pass channel with a bleed hole, which is applicable to the internal cooling passage of typical gas turbine blade. The bleed hole is placed on the tip wall of a two-pass channel at different locations, i.e. the ratio of distance from the outlet-side wall to width of the tip wall is 0.07, 0.21, 0.5, 0.78, 0.93, respectively. A smooth channel without bleed hole is used as Baseline. The Reynolds number is fixed at 10,000. The Ro numbers are varied from 0 to 0.4. Results show that a three-dimensional vortex, which is induced by the Coriolis force, is found at the bend region. It transports the fluid from the trailing side to leading side, which is beneficial to enhance tip heat transfer. The middle-mounted hole shows a better heat transfer augmentation compared to other hole arrangement. The rotation have a notable effect on the heat transfer and flow structures. Compared to the smooth channel, the heat transfer augmentation is about 34%.

Due to the influence of an adverse pressure gradient, three types of flow separation occur on the suction surface of a linear compressor cascade: full-span open separation, corner closed separation and a corner stall condition. A numerical simulation was performed using a topological analysis method to determine the applicability of using a curved blade to improve the total pressure loss coefficient of a cascade with different types of flow separation situations on the suction surface. First, the accuracy of the ANSYS CFX program was verified against existing experimental data to balance the relationship between the calculation accuracy and the time savings. Second, the incidence characteristics of the cascade were analyzed to determine the incident conditions for three types of flow separation. Three factors of the cascade were considered to analyze a cascade with and without a curved blade: the transferring process of the topological structure on the blade suction surface, the evolution process of the vortex structure in the cascade passage and the weight distribution of the total pressure loss coefficient. The results indicate that the strength and scale of the concentrated shedding vortex (CSV) is distinctly reduced in the corner stall condition due to the influence of radial migration by the curved blade; thus, the flow loss is observably reduced. In the corner closed separation condition, the scale of the corner separation was too small to be notably reduced. In the full-span open separation condition, the curved blade not only reduced the total pressure loss coefficient but also increased the strength and scale of the passage vortex (PV). Finally, the curved blade method improved the applicability of reducing the flow loss in the corner stall condition and increased the stability and margin of a highly loaded compressor.

High thermal load on the turbine blade tip surface would lead to high temperature corrosion and severe structural damage. One method to reduce blade tip high thermal stress is to use cooler fluid from the compressor, that exists dirt purge hole mounted on the tip underside, for cooling purpose. In this study, internal serpentine cooling passage is modeled as a U bend channel with a sharp 180-deg turn with the dirt purge hole arranged at the tip-wall. The effect of the layout of dirt purge hole and varying coolant mass flow rate on flow structure, heat transfer on the tip-wall and friction factor of the U bend channel are numerically studied with Reynolds number ranging from 100,000 to 440,000. The results show that the vortex pair is forced to flow near the tip-wall while the increasing shearing effect induced by the vortex pairs increases the local heat transfer. With an increase mass flow rate of the dirt purge hole, the suction effect enhances the local heat transfer performance. However, the pressure loss is also increased accordingly at all Reynolds numbers. The augmentations with Reynold analogy performance and the thermal performance for 5.8% mass flow rate case is 12.5% and 12.7%, respectively, which reaches the highest performance augmentation compared to the smooth-tip channel.

In this study, numerical simulations are performed to investigate the effect of the dimple/ protrusion depth on the flow structure and heat transfer characteristics in a rotating channel with pin fins. The pin fins are arranged with staggered layout. The longitudinal and transverses pitches of the pin fin are 2.5. The dimples/protrusions are located on the endwall surface between the pin fins. The print diameter of the dimple/protrusion is same as the pin fin. Five different dimple/protrusion depth-to-diameter ratios are investigated, i.e. δ/D = 0, 0.1, 0.2, 0.3, 0.4. Results of the flow structure, heat transfer on the endwall are included in this study. It is found that the flow structure and heat transfer are sensitive to the rotational Coriolis forces, both on the leading side and trailing side. In the dimpled channel, the area of the low-speed recirculation is increased as the dimple depth increased. The trailing side has higher pressure and TKE compared to the leading side. In addition, the Nu number is high at the trailing side due to the Coriolis forces. In protrusion channel, the pressure is increased at the front of the protrusion as the protrusion depth increases. A counter-rotating vortex is found at the top of the protrusion. The Nusselt number is also higher at the trailing side compared to the leading side.

Jet impingement cooling is widely used in modern gas turbines. In the present study, both heat transfer and flow field measurements of jet impingement in cross-flow are carried out with and without a vortex generator pair (VGP). The jet and cross-flow Reynolds numbers are fixed at 15,000 and 48,000, respectively. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. Results show that the jet impingement heat transfer on the target wall is remarkably enhanced by the VGP as compared to the baseline case. The stagnation region moves upstream with improved heat transfer when the VGP is present. The flow field is measured by particle image velocimetry (PIV). The cross-flow is shown to deflect the impinging jet but the VGP reduces the streamwise momentum of the cross-flow and drives the crossflow away from the issuing jet. This leads to stronger jet impingement and thus heat transfer enhancement on the target wall.

The two-dimensional coupled implicit RANS equations and three turbulent models have been employed to numerically simulate the nonreacting and reacting flow fields of a typical strut-based scramjet combustor, and the numerical results have been compared with the experimental data. At the same time, three different grid scales have been used to test the grid independence in the numerical simulations, namely the small scale (81,590 nodes), the moderate scale (98,510 nodes) and the large scale (147,470 nodes). The obtained results show that the RNG k-ε model is more suitable to numerically simulate the flow field in the scramjet combustor than the realizable k-ε model and the SST k-ω model, and the numerical results obtained by the moderate and large grid scales show reasonably better agreement with the experimental data. The quasi-diamond wave system is formed in both the nonreacting and reacting flow fields. In the reacting flow field, there are two clear strong shear layers generated between the fuel injection and the supersonic freestream, and at the intersection point between the shear layer and the reflected shock wave, the reaction zone is broader than anywhere else. In the corner formed between the upper surface of the strut and the shear layer, an expansion wave is clearly generated, and another also exists in the symmetrical corner.

Plate fuel assemblies will be widely applied in the future because of their simple and compact structure and excellent heat exchange capability. When the plate fuel assemblies are used in a ship reactor, the effect of the ship motion on the reactor core thermal hydrodynamic must be investigated. In this paper, aiming at the rectangular shape of coolant channels in the assemblies, the numerical simulation of the flow and heat exchange in a rectangular channel in horizontal translation is carried out. Using the CFD Software and UDF code, the simulation model of the channel in horizontal translation with and without acceleration along its width direction is built up, and the related characteristics is analyzed and discussed. The results and conclusions are applicable and useful for the new type ship PWR design.

According to the specific structure of a marine reactor pressurizer and its operating characteristics of frequent pressure and water level fluctuation, a new non-equilibrium four region mathematical and physical model is established for the first time to fulfill the aim of fast and precise simulation. The model includes the bubble rising, condensate dropping, wall condensation and heat transfer through outside wall while the heat and mass transfer at the liquid and gas interface is neglected. The initializing program is also introduced. The Simulink is adopted as the simulating tool and the corresponding Simulink module is established. The simulation proves to be very fast in a common microcomputer, which indicates that Simulink is efficient and is suitable for the fast simulation of marine reactor with the characteristics of frequent variations of power and corresponding physical and thermal parameters. A typical process with surge flow varying very acutely and complicatedly is adopted as an example. The variation of the pressure and the water level of the process by the new model agree well with the results of Relap5/Mod3.3, which proves the validity of the model and some simplification adopted. As one of the main parts of the fast simulation program under development for in the operating field use for a marine nuclear power plant, the achievement of the fast simulation of the pressurizer is of significant importance.